CCNet, 79/2000 -  15 August 2000

     "According to NASA scientists, the hunt for large asteroids that
     might collide with Earth has reached a milestone -- it is
     estimated that about half of these giant space rocks have now been
     found. [...] The claim that a milestone has been reached is
     expected to draw a mixed reaction from scientists. Also, smaller
     NEAs and fast-moving comets are still a threat. A collision by a
     NEA just 200 yards (180 meters) across could devastate a small
     country, disrupt global weather for months and, perhaps, bring
     down the global economy."
        -- Michael Paine, 7 August 2000

     "The swift and untimely breakup of the doomed Comet Linear is much
     more than simply a curious celestial fireworks show. For the first
     time in history, astronomers have gotten a detailed look  at how
     the amalgam of dust and ice in a comet nucleus is actually
         -- Ray Villard, 11 August 2000

    SpaceDaily, 15 August
    Andrew Yee <>
    Ron Baalke <>
    Mr. X <>

    National Post, 12 August 2000


From SpaceDaily, 15 August
China Builds New Observatory To Detect Near-Earth Asteroids

by Wei Long

Beijing - August 15, 2000 - China began the construction of a new
astronomical observatory dedicated to the detection and study of
near-Earth asteroids (NEAs), Xinhua News Agency reported on August 3.

According to Yang Jiexing, an astronomer who is in charge of the
project at the Purple Mountain Observatory in Nanjing, the new
observatory is being built in the Tieshanshi State Forest Park in Xuyi
County in the eastern Jiangsu Province.

The chosen location has an unobstructed view of the horizon and a very
dark sky, with the number of clear nights reaching 210 in a year.

The observatory will house a telescope with a mirror diameter of 1.2
metres to observe near-Earth asteroids and comets. The observations
will be used to determine precise orbits of these objects and find out
if they pose any threat of colliding with Earth in the future.

Completion of the observatory is planned for 2002. The estimated cost
of the project is more than 10 million yuan renminbi ($1.2 million US).
Funding comes from the local government, the State science and
technology department, and contributions from Hong Kong.

Upon completion the new observatory will join an international network
of observatories to monitor near-Earth objects.

Since the mid-1990s China has been active in studying asteroids. The
Xinglong Station of the Beijing Astronomical Observatory (BAO), which
is about 180 km northeast of Beijing, is among a dozen observatories in
the existing asteroid monitoring network. Here the Schmidt telescope,
which is smaller than the telescope that will go in the new
observatory, is equipped with a CCD camera to observe minor planets
under the Schmidt CCD Asteroid Program (SCAP).

SCAP found its first NEA, 1997 BR, on January 20, 1997. As of January
this year SCAP is credited with discovering five NEAs, two of which are
potentially hazardous asteroids (PHAs).

Copyright 2000, SpaceDaily


From Andrew Yee <>

[ ]

Friday, 4 August 2000

When it's cool to be cool

Not everyone loses out when the sky falls in. Two almost simultaneous
giant meteorite impacts 35 million years ago boosted the abundance of
some marine microorganisms, a report in Geology [1] now suggests,
despite triggering a cold spell that lasted about 100,000 years.

Long blamed for the demise of the dinosaurs 65 million years ago, the
re-emergence of giant meteorite impacts on Earth in Hollywood movie
plots stems from astronomers' growing realization that there are still
many threatening lumps of rock out there in the Solar System.

The idea that meteorite impacts can cause a world-wide drop in
temperature stems from work on another Armageddon nightmare: nuclear
war. In the early 1980s, astronomers and climatologists suggested that
the vast amounts of dust that would be thrown into the atmosphere by
nuclear explosions would shield the planet from sunlight and cause
near-ice-age conditions.

Hubert Vonhof of the Free University of Amsterdam, the Netherlands, and
his co-workers wondered whether two giant impacts that happened in the
late Eocene epoch, about 35 million years ago, might have had similar

These catastrophic events were discovered when researchers found tiny
mineral spheres -- 'spherules' -- in rocks that were deposited as ocean
sediments all that time ago. Called 'tektites', the spherules are
characteristic markers of a giant impact, being the remnants of molten
rocky debris ejected when a meteorite strikes.

There are two areas strewn with tektites from this time, which
geological dating techniques show to differ in age by about
10,000-20,000 years. In geological terms this makes the impacts almost
contemporaneous, and means that their combined effects on the global
environment could have been much greater than either alone.

In the 1990s a crater was discovered in the sea bed beneath Chesapeake
Bay, which was suggested as the site of one of these Eocene impacts. A
few years later a second crater at Popigai in northern Siberia was
found and assigned as the possible source of the other tektites. Both
craters are around 100 kilometres across, and could have been caused by
meteorites a few kilometres in diameter.

The meteorite that struck 30 million years previously, possibly wiping
out the dinosaurs, seems also to have caused extinctions amongst many
other kinds of life on land and sea. But there is no indication in the
fossil record that the two Eocene impacts were so deadly.

Vonhof and colleagues analysed the geological record as imprinted in
sedimentary rocks drilled from the floor of the Southern Ocean, near
Antarctica. By measuring changes in different isotopes (atoms with
different mass) of oxygen within the shells of microscopic marine
creatures called 'forams', they were able to deduce how temperatures
had changed over the period during which the rocks were deposited. They
found a rapid drop in temperature, of about 2 C, 35.5 million years ago
-- when the two impacts occurred.

The cooler temperatures somehow favoured marine life: forams apparently
flourished at this time. And at least one species of 'dinoflagellates',
another microscopic organism, also seems to have thrived after the

These biological changes, the researchers suggest, were caused by
changes in ocean circulation, which made the waters more nutrient-rich.
But cooling appears to have lasted for around 100,000 years, which is
much longer than can be explained by impact dust.

Vonhof's group suggests that the dust-induced cooling caused a build-up
of ice and snow cover, leading to a positive feedback effect on global
cooling that locked the world's climate into a longer-term cold spell.

[1] Vonhof, H. B., Smit, J., Brinkhuis, H., Montanari, A. & Nederbragt,
A. J. Global cooling accelerated by early late Eocene impacts? Geology
28, 687-690 (2000).

© Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE


From, 7 August 2000
By Michael Paine
Special to

According to NASA scientists, the hunt for large asteroids that might
collide with Earth has reached a milestone -- it is estimated that
about half of these giant space rocks have now been found.

NASA's goal is to find 90 percent of "Near Earth Asteroids" larger than
1000 yards (1 kilometer) by 2009. In recent years the discovery rate
has improved dramatically. In figures just released by NASA, the LINEAR
system in New Mexico still dominates the discovery statistics.

Near Earth Asteroids (NEA) orbit the sun in the same region as Earth.
But in most cases, the orbits are highly elongated and stretch out to
the asteroid belt between Mars and Jupiter. Recent estimates suggest
there are about 900 of these objects larger than 0.6 mile (1 kilometer)
in diameter. A collision with a space rock of this size could destroy
civilization. In an e-mail newsletter posted this week, David Morrison
from NASA reports that 410 large NEAs have now been found. He points
out that this is just past the halfway mark -- assuming that the
90-percent goal is achieved when 810 large NEAs have been found.

This may be a halfway point when measured by the number of objects
discovered, but this is not the same as measuring the time it takes to
reach the goal. Although the graph of discovery rate suggests this goal
can be achieved by 2009, the task will become more difficult once the
remaining easily-detected NEAs have been found. More telescopes will
probably be needed to keep the graph on target.

The claim that a milestone has been reached is expected to draw a mixed
reaction from scientists. Also, smaller NEAs and fast-moving comets are
also still a threat. A collision by a NEA just 200 yards (180 meters)
across could devastate a small country, disrupt global weather for
months and, perhaps, bring down the global economy.

Earlier this year NASA's Don Yeomans told "The current
[NASA] plan is to find the big ones first, then as the detection
technology improves, extend the search to smaller and smaller objects."

But it would likely take a major international effort to find a good
proportion of the remaining threatening objects. Scientists are
concerned about a lack of a major international program to follow-up on
discoveries and to ensure they are not lost. In the words of astronomer
Duncan Steel, "It is like throwing the needles back into the haystack."

Copyright 2000,


From Ron Baalke <>


Contact: Jeffrey Larsen, 520-621-3384,
(Note: Larsen can be contacted by e-mail during the meeting)

August 11, 2000

(Writer: Agnieszka Przychodzen for UA News Services, 520-621-1877)

MANCHESTER, England -- When Clyde Tombaugh discovered the planet Pluto
70 years ago, the picture of the solar system seemed clear and orderly.
It showed our central star, its nine planets, the asteroid belt, and
comets visiting occasionally from the dark and chilly fringes of the
solar system. Today, thanks to the pioneering asteroid survey
Spacewatch and similar projects, our planetary system appears as a
humming hive populated with countless asteroids circling the sun like a
swarm of bees.

Jeffrey Larsen, a principal research specialist with the Spacewatch
group at the University of Arizona (UA) Lunar and Planetary Laboratory
in Tucson, and his undergraduate students recently used the
80-year-old, 36-inch Spacewatch telescope on Kitt Peak in discovering
dim Centaur asteroids and Trans-Neptunian Objects (TNOs).

Larsen is talking about it today at the 24th General Assembly of the
International Astronomical Union in Manchester, England.

Centaurs orbit between Jupiter and Neptune, typically 5 to 30
astronomical units (AU) away. (An AU is Earth-to-sun distance.) "Their
orbits are very elliptical and cross the orbits of these planets, so if
anybody lived on Jupiter these objects would be as close as Near Earth
Asteroids (NEAs) are to Earth, " Larsen explains. "Centaurs also seem
to be related to comets. From the point of view of their orbits, you
cannot tell the difference between the two. Comets get comas and tails
as they get closer to the sun, Centaurs never do."

Trans-Neptunian Objects are even more remote. They circle the sun at a
distance of at least 38 AU in circular orbits comparable with Pluto's

"There are at least as many of them in Pluto¹s vicinity as have been
found in the main asteroid belt, a region between the orbits of Mars
and Jupiter. TNOs are very difficult to spot because they are very
distant," says Larsen.

Larsen and his students looked 20 degrees above and below the plane of
the ecliptic, or the plane through which the planets circle the sun,
using the 36-inch Spacewatch telescope, the oldest telescope on Kitt
Peak. They also analyzed data collected previously by Spacewatch to
locate the extremely dim objects from between 24 and 27 magnitude. (By
comparison, Jupiter seen from Earth is bright, or at minus 2

During Spacewatch observations May through August 1999, Nichole Danzl,
Arianna Gleason, and graduate student Anne Descour discovered five
TNOs, three Centaurs and two 'scattered disc objects'. These asteroids
wander between 40 and 150 AU, or farther away than Pluto.

To complicate the matter even more, the team also discovered two
asteroids that met both criteria - they crossed planetary orbits like
Centaurs and wandered far away from the solar system like scattered
disc objects. Based on these two discoveries, the Centaurs and
scattered disc objects are now considered a single class of asteroids.

Spacewatch astronomers search for asteroids by taking repeated scans of
certain patches of the sky. Such scans are six-tenths of a degree wide
(approximately as wide as the full moon) and about 12 full moons long. It
takes a CCD detector about 30 minutes to acquire a single image. The
astronomers then compare images taken at different times. If there is
an asteroid in any of the images, it will appear to ?move¹ across the
picture. Asteroids travel at different rates, depending on where they
are in the solar system.

"Near Earth Asteroids move between three-tenths of a degree to 30
degrees a day. Main belt asteroids at opposition (when the asteroids
are on the opposite side of the Earth as seen from the sun) move on
average about two-tenths of a degree a day. Trans-Neptunians are so
distant that, when observed from the Earth, they seem to barely move at
all, " Larsen says.

UA astronomers Tom Gehrels and Robert McMillan, who currently leads
Spacewatch, founded the Spacewatch Project in 1980 to survey for
asteroids and comets that might pose a threat to Earth.

The 1989 discovery of Chiron - known now to be a Centaur asteroid -
came as a surprise.. Originally, astronomers assumed that it was just a
single object drifting on the outskirts of the solar system.  But in
1991 Spacewatch observers found the second Centaur, Pholus.  Today a
whole population of 16 Centaur asteroids is known, and Spacewatch
discovered about half of them.

In 1992 astronomers David Jewitt of the University of Hawaii and Jane
Luu of the University of California ­ Berkeley discovered the first
Trans Neptunian Object, an object named 1992 QB1 which orbits the sun
at about 40 AU. "That was further away than Pluto and proved that
asteroids inhabit even the farthermost parts of the solar system,"
Larsen says.

These distant bodies may hold the key to the origin of our planetary
system. What intrigues astronomers is their peculiar location in the
solar system. They are at the same distance from the sun as
protoplanetary discs surrounding very young stars, such as Beta
Pictoris. By mapping Centaurs and TNOs, learning how abundant they are
and how they are distributed, theorists hope to form a model of how the
solar system came into existence.

"The other reason why the brighter of these objects are important is
that they are the easiest to study with spectroscopy, " Larsen says. 
Spectroscopy reveals the chemical composition of objects, and by
asteroid spectra astronomers may be able infer the composition of the
primordial solar nebula.

Also, the physical rules that triggered the solar system's formation
and how long that process took remain a mystery. Hidden near at the
periphery of the solar system, many TNOs have not been influenced by
the gravitational forces of planets, especially Jupiter. Their orbits
may represent the original configuration of matter in the very early
solar system.

"The size distribution of these bodies is important for making models
of the solar system's formation. Whatever the original protosolar
nebula was doing, the TNOs probably have some signature of it left in
their orbits," Larsen says.

After the discovery of Pluto, astronomers looked without success for
similar objects. Many then thought that Pluto was unique and,  apart
from the Oort Cloud of comets beyond Pluto, believed that the outer
solar system was devoid of any sizable objects.

"Today the picture looks more messy. Our solar system seems to be
populated with many objects that even a few years ago were not seen
because they are extremely faint. We still do not know yet how far out
they go, " Larsen says.

Spacewatch cannot presently look far enough to see the most distant
objects that may exist.

"We are only able to see the inner rim of the TNO belt. Nobody has
found objects in circular orbits past 50 AU.  Does this mean the belt
ends at that distance? The scattered disc objects exist past 50 AU,
though we have not discovered many of them. I'll be willing to bet
money that we just haven't looked right," Larsen speculates.

***Spacewatch web page @ ****


From, 11 August 2000

By Ray Villard

The swift and untimely breakup of the doomed Comet Linear is much more
than simply a curious celestial fireworks show.

For the first time in history, astronomers have gotten a detailed look
at how the amalgam of dust and ice in a comet nucleus is actually
packaged. This comes from spectacular close-up pictures taken several
days ago by the Hubble Space Telescope and follow-up observations by
the Very Large Telescope in Chile. Hubble first showed that the icy
nucleus - the fountainhead of the comet's gossamer tail -- fell
apart into a cluster of "mini-comets." Each fragment is probably
smaller than a football field.

Seeing the "subassembly" of a comet nucleus provides a clear blueprint
of the internal structure of comets and helps settle the debate over
whether they are flying "gravel piles," or are built up from
consecutively smaller pieces, like the Russian Matrushka toy of nested

Comet together

The comet's solid nucleus was assembled from these mini-comets -- or
cometesimals -- at about the time of the birth of the planets in our
solar system 4.5 billion years ago. Seeing the comet come apart in such
fine detail is like opening a time capsule containing the long-sought
relics of the early solar system.

In estimating the number of planets in our galaxy, astronomers need to
know how they formed around stars. Astronomers have seen both ends of
the planet construction process. They've cataloged over 50 extrasolar
planetsand Hubble has surveyed over 100 embryonic disks of fine dust
around stars out of which the planets will presumably condense. But the
process itself cannot be seen, so astronomers must look for fossil
evidence within our own solar system.

Like the planets, comets were built up from micron-sized grains of dust
no larger than the thickness of a human hair. Over tens of millions of
years, the dust clumped together with ice to form snowball-like frozen
bodies measuring dozens of feet (meters) wide.

These "cometesimals" gently merged, sticking together to build up 
comet nuclei, which then grew to a few miles (kilometers) across. 
Some of these nuclei continued to coalesce to form the icy solid
cores of the gas-giant planets. Once the giant planets formed,
they gravitationally captured or tossed the remaining comet nuclei
out of the solar system to create the Oort cloud.

Valuable clues

Knowing how comets are put together offers clues on how to deflect
or destroy a wayward comet that might collide with Earth.

Copyright 2000,


From Mr. X <>

Dear Dr. Peiser,

I have noted a few references to my own web-site (at
in the CCNet. I'd note that some references to events in 1737 mention a
fireball over Kilkenny, Ireland; however, when I researched this event,
I discovered the "fireball" was apparently an auroral display seen over
much of Europe. This is found in my footnote, at:

as follows:

"Am. Guillemin. "Sur deux observations qui paraissent offrir quelque
analogie avec celle du météore signalé récemment par M. Coggia."
Comptes Rendus, 73 (1871): 755-6. Guillemin provides no duration nor
the date of an object seen over Paris in 1853; and, he claims "a globe
of fire" was observed over Kilkenny, Ireland, for an hour, on December
26, 1737. However, the date of this observation was December 5, 1737,
(not December 26); on this date, a red-coloured auroral display was
observed across much of Europe, from Italy to Scotland; and, it is
described thus: "This same Phænomenon was of great Extent in the
Northern Parts of Europe; and at Kilkenny in Ireland, was seen somewhat
like a Globe of Fire suspended in the Air for near space of an Hour;
which then bursting, spread Flames around on every Side." Thomas Stack.
"An account of a book intitled, Observationes de Aere & Morbis
Epidemicis...." Philosophical Transactions of the Royal Society of
London, 40 (December 1738; n.451): 429-40, at 437-8. "A collection of
the observations of the remarkable red light seen in the air on Dec. 5,
1737, sent from different places to the Royal Society." Philosophical
Transactions of the Royal Society of London, 41 (January-March 1741;
n.459): 583-606."


Mr. X


From National Post, 12 August 2000

By Robert Mendelsohn
National Post

When negotiators at the 1997 Kyoto convention on climate change set out
to establish limits on greenhouse gas emissions by industrialized
countries and create incentives for developing countries to control
theirs, the potential gains of climate change were hardly mentioned.
Countries simply assumed that slowing global warming would produce
widespread benefits, and would justify the investments made by each
treaty signatory.

Except for the handful of island nations that view global warming --
and the subsequent rise in the sea level -- as a threat to their very
existence, nobody seemed particularly concerned about the differential
impact of climate change. Yet the scientific evidence amassed over the
past five years raises serious issues about these benefits.

First, the estimated magnitude of the benefits from controlling
greenhouse gases has fallen. While less warming is still thought to be
preferable to more, there is now a lot more reason to doubt that the
most expensive control programs -- the ones aimed at the high-hanging
fruit -- are worth the expense.

Second, the distribution of the potential benefits from containing
emissions is clearly not uniform among countries, or even among regions
within large countries. Countries closest to the poles -- notably
Russia and Canada -- and even temperate countries such as the United
States and Western European nations are now expected to benefit from
warming. Only the tropical countries are likely to suffer

Why have damage estimates fallen? Early studies vetted by the
blue-ribbon Intergovernmental Panel on Climate Change (IPCC) -- based
on estimates that temperatures would rise four degrees to six degrees
centigrade by 2060 -- forecast that by that year, unchecked climate
change would reduce global economic output by 1% to 3%. This level of
damage justified a modest investment in containing greenhouse gases
today, and larger investments later on.

Based on new data plugged into more sophisticated models of temperature
transmission in the oceans, the most recent IPCC climate report
forecasts increases of just 1.5 degrees to 4.5 degrees by 2100.

Although the original studies correctly assumed that temperature change
would alter the ecology, they failed to note that the consequences for
economic productivity would not always be negative. For example,
initial findings indicated that climate change would heavily damage
regional ecosystems. Whether the ecosystems were crops, forests or
grassland, the studies predicted that productivity would fall,
and some systems would actually "collapse."

But new data suggests global output is likely to increase as carbon
dioxide builds up, and many of the ecosystems that cannot tolerate
climate change will probably be replaced by new ones that better serve
the economic interests of the human population.

Earlier predictions also forecast ecological catastrophes that would
transform parts of the Earth into moonscapes. The new predictions
envision an expansion of tropical and boreal forest toward the two
poles. Of course, any global change of this magnitude would involve
local changes that are both good and bad; it is hard to assay the
overall impact of such a broad change with models that rely on the
limited data now available. The critical point, though, is that the
movement of biomes across space is not necessarily threatening to
people or even to nature.

As many of the earlier impact assessments focused solely on the damages
from warming -- the need for increased electricity for cooling, the
deaths of elderly people caught in heat waves -- offsetting benefits
were conspicuously missing from these analyses. The energy studies
ignored the savings in oil and natural gas no longer needed for
heating. The agricultural studies failed to include heat-loving plants
that would do exceptionally well in a warmer world. The recreational
studies overlooked the prospects for summer activities such as swimming
off the beaches of Oregon or fishing in northern lakes. The health
studies overlooked the fact that the elderly often live longer in warm

These estimated benefits have turned out to be surprisingly large; if
they are included, the net economic impact of global warming turns

Initial studies generally overlooked the potential for economic
adaptation and simply assumed that climate change would happen
overnight, when in fact the change would unfold gradually over the
century. And over a century, farmers would be able to switch crops
and move heat-sensitive crops poleward.

This is not Pollyanna talking. Over the past 150 years, equivalent crop
migrations have taken place relatively effortlessly. Farmers shifted
the American grain belt hundreds of miles westward in response to
changing transportation costs. Farmers can also adapt by changing
planting dates, harvest times, tilling strategies and plant varieties.
Biotechnology can help, too, by modifying plants for temperature and
rainfall. This sort of adaptation would not only reduce crop damage in
places that get too warm, but also increase net revenues in places that
are currently too cool.

Similarly, adaptation strategies in every other market sector affected
by climate-linked change would dramatically reduce damages. Sea walls
could be erected gradually over the next century to protect vulnerable
coasts from rising sea levels. A careful model of the way forests would
actually change in the face of climatic stress suggests that many of the
trees could be harvested and replaced as part of normal forestry
operations. In fact, a gradual warming would allow more productive
forests to replace existing stands and actually increase timber

Water shortages in growing metropolitan areas located in semi-arid
regions can be avoided merely by taking water away from lower-value
uses -- a process that could be facilitated by pricing water according
to its "opportunity cost." Reductions in runoff in semi-arid places
would presumably still lead to ancillary environmental damage -- but
hardly the spread of deserts envisioned by the first generation of
global warming studies.

First-generation damage estimates that once were a good reason for rich
countries to press for a global warming treaty have since become
net-benefit estimates that actually create incentives for delay. New
estimates of annual damages in the developed world due to warming even
show small net gains (perhaps 0.1% of output).

Even transition economies located in cool latitudes -- for example,
China and the former Soviet bloc countries -- have a good shot at
winning the global-warming lottery. Indeed, the latter countries are
expected to gain between US$86-billion and US$228-billion annually.
China, which straddles warm and cool latitudes, would gain an expected
US$14-billion to US$42-billion from warming.

Of course, not every country would be better off. Of all the regions in
the world, tropical countries have the greatest direct incentive to
push for reductions in greenhouse gas emissions -- but these countries
effectively boycotted the Kyoto agreement, and influencing the process
now won't be easy.

As very little climate impact research has been undertaken in tropical
countries, there is a great deal of uncertainty about the potential
impact of warming in areas where much of the world's population is

One thing is certain: Our growing knowledge about the process of global
warming is likely to complicate negotiations over how much to limit
emissions and how to pay for the controls. Indeed, once reality sets
in, the developed countries may be quite content to argue about treaty
details indefinitely before implementing a binding agreement.

As for developing countries, it is one thing for them to acknowledge
that greenhouse gases are a threat to their interests and quite another
to ask their citizens to accept lower rates of economic growth today in
order to spare their grandchildren the uncertain consequences of global
warming. The outcome may well be one of little collective action.

And so it appears that the world is about to undertake a massive
greenhouse gas experiment. Carbon dioxide levels will likely continue
to increase, testing the resilience of the planet's biosphere. Although
it is impossible to guarantee that good things will come to pass over
the next century, the forecasts are decidedly cheerier than they were
five years ago.

Robert Mendelsohn is the Edwin W. Davis Professor of forest policy at
Yale University's School of Forestry and Environmental Studies. This is
adapted from an article first published by the Milken Institute Review.

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